This invention relates generally to a clutch/brake unit and, more particularly, to a clutch/brake unit for use with a machine such as a walk-behind lawn mower. In a clutch/brake unit of this type, the clutch normally is disengaged to uncouple the cutting blade from the drive shaft of the engine and, in addition, the brake normally is engaged to prevent rotation of the blade. When a manual control such as a deadman lever is actuated, the clutch is engaged and the brake is released so as to permit driving of the blade.
A clutch/brake unit of the same general type as the unit of the present invention is disclosed in Takata et al U.S. Pat. No. 4,377,224. In the clutch/brake unit of the Takata et al patent, an input hub rotates with the drive shaft of the engine of the mower while an output hub is supported to rotate relative to the shaft. A friction plate is coupled to rotate with and move axially relative to the output hub and is spring-biased into engagement with the input hub. When the clutch is engaged, the input hub rotates the output hub by way of the friction plate.
The Takata et al unit also includes a braking element which is supported to move axially relative to the input member. When the deadman control is manually released, a rotary actuator is turned in one direction and acts through a series of angularly spaced balls to cam the braking element axially into engagement with the friction plate. This applies a braking force to the output hub and, at the same time, forces the friction plate out of engagement with the input hub so as to interrupt the drive from the input hub to the output hub. When the deadman lever is manually actuated, the rotary actuator is turned in the opposite direction, the braking member releases the friction plate, and the friction plate transmits torque from the input hub to the output hub.
In order for a clutch/brake unit of the foregoing type to function properly, it is necessary that the braking element be held against rotation. Also, it is necessary that the braking element be biased toward the rotary actuator so that, when the brake is released, the braking element will act to reset the balls into proper angular positions for the next brake-engagement/clutch-disengagement step. In the clutch/brake unit of the Takata et al patent, rotation of the braking element is prevented by a plurality of angularly spaced bolts which extend through the braking element and which are threaded into the lower end of the engine. Coil springs are telescoped over the anti-rotation bolts and are compressed against the braking element in order to bias the latter toward the rotary actuator.